The geopolymeric alumino-silicates have been grouped in three families depending on the atomic ratio Si/Al which may be 1, 2 or 3. With the most commonly used simplified notation, a distinction is made between
______________________________________ poly M.sub.n --(Si--O--Al--O) .sub.n-- or (M)--PS, (sialate) poly M.sub.n --(Si--O--Al--O--Si--O) .sub.n-- or (M)--PSS, (sialate- siloxo) poly M.sub.n --(Si--O--Al--O--Si--O--Si--O) .sub.n-- or (sialate- (M)--PSDS disiloxo). ______________________________________
In several scientific papers, for instance "Geopolymer: room temperature ceramic matrix composites" published in Ceram. Eng. Sci. Proc., 1988, Vol. 9 (7-8), pp. 835-41, cf. Chemical Abstracts 11O-080924, or "Geopolymer Chemistry and Properties" published in Geopolymer '88, Vol. 1, pp. 18-23, University of Technology, Compiegne, France, or the international patent publication WO 88/02741 (U.S. Pat. No. 4,888,311), the prior art discloses the uses of poly(sialates) Mn(--Si--O--Al--O), (Na)-PS/(K)-PS and poly(sialate-siloxo) Mn(--Si--O--Al--O--Si--O--), i.e. (Na)-PSS/(K)-PSS. It does not deal with any process for producing poly(sialate-disiloxo) Mn(--Si--O--Al--O--Si--O--Si--O--)n, i.e. (M)-PSDS.